The FSGS Cohort Study is a prospective, longitudinal cohort study designed for long-term assessment of the NIH sponsored Focal Segmental Glomerulosclerosis Clinical Trial (FSGS-CT) participants. The FSGS-CT randomized 138 children and young adults with primary FSGS and will be completed on November 30, 2009. The goal of the FSGS Cohort Study is to extend the observation of the randomized trial participants to document the long-term kidney survival. This follow-up will contribute immensely to the productivity of the NIH investment in the FSGS CT by extending the outcome from one based upon a surrogate (proteinuria response) to one based upon a robust outcome of prospectively documented kidney failure. A prolonged, protocol-based observation period will enable systematic evaluation of the impact of the trial's randomized intervention, changes in patterns of proteinuria, and postulated disease progression risk factors on the occurrence of robust outcomes [such as reaching End State Kidney Disease (ESKD)] that directly influence patient well being and survival. Furthermore, the FSGS Cohort Study will provide the opportunity for to extend our knowledge of the pathobiology of FSGS through the FSGS ancillary study mechanism and through ongoing multi-investigator collaborations. PUBLIC HEALTH RELEVANCE: A major mission of the NIH/NIDDK is alleviating the burden of ESKD on the U.S. population, and in particular, on those most vulnerable to progressive kidney disease, i.e., children and populations at risk for health care disparities. The FSGS Cohort Study offers the opportunity to extend the goals of FSGS-CT by maintaining data collection for long-term patient follow-up. Its unique data will allow investigation of the natural history and etiologies of FSGS and of treatments to prevent progressive renal disease in FSGS patients.